Cold dark matter: The hunt for the axion

Transcription

1 SQUIDs: Then and Now SQUIDs: Then SQUIDs: Now The diversity of SQUIDs Ultralow field magnetic resonance imaging Cold dark matter: The hunt for the axion History Day Superconductivity Centennial Conference Den Haag The Netherlands September 21, 2011 Support: DOE Basic Energy Sciences DOE High Energy Physics National Institutes of Health BBN Technologies 1 of 45

2 SQUIDs Then 2 of 45

3 Brian Josephson Explains Tunneling Courtesy Brian Josephson 3 of 45

4 Flux Quantization = n 0 = n (n = 0, ±1, ±2,...) J Half-centennial! where 2x h/2e Tm is the flux quantum Vibrating s/c tube in a coil Torque on a s/c tube Deaver and Fairbank 1961 Doll and Näbauer of 45

5 Josephson Tunneling I Insulating barrier Superconductor 1 Superconductor 2 I Sn-SnOx-Pb SO 1.5 K ~ 20 Å V I = I 0 sin = 1 2 d /dt = 2eV/ħ G = 2 V/ G Josephson 1962 Half-Centennial Next Year! Anderson and Rowell of 45

6 Birth of the Superconducting Quantum Interference Device (SQUID) I V Sn-SnOx-Sn junctions Critical current versus applied magnetic field for two different junction spacings Rapid oscillations due to interference, slow oscillations due to diffraction Essential physics analogous to two-slit interference in optics Jaklevic, Lambe, Silver and Mercereau of 45

7 Sir Brian Pippard Serves Tea to Lady Bragg Autumn 1964: Brian suggests that t a SQUID would make an exquisitely sensitive voltmeter Courtesy Cavendish Laboratory 7 of 45

8 The SLUG (Superconducting Low-Inductance Undulatory Galvanometer) Nb wire and solder I Niobium I B I Copper Vo oltage V SnPb solder 5 mm Current I B in niobium wire I B JC February of 45

9 The SLUG as a Voltmeter Niobium 1 Voltage noise 10 fvhz -1/2 Copper V Solder 5 mm 9 of 45

10 John Wires up a SLUG Courtesy Gordon Donaldson 10 of 45

11 Other SQUID Designs Niobium structures Zimmerman and Silver of 45

12 Adjustable Niobium SQUID Nb wire and foil 0.03 Nb wire Nb foil mylar Beasley and Webb of 45

13 Nb-NbOx-PbInNbOx junctions Shadow masks Thin-Film Cylindrical SQUID 5 mm tesla Hz -1/2 (10 fthz -1/2 ) Goubau, Ketchen, JC of 45

14 SQUIDs Now 14 of 45

15 Nb-AlOx-Nb Tunnel Junctions Trilayer process Deposit Nb film as base electrode Deposit Al film Grow AlOx layer thermally in O 2 Deposit Nb film as counter electrode ect Standard d process for all low-t c electronics Rowell et al of 45

16 Thin-Film, Square Washer DC SQUID Wafer scale process Photolithographic patterning 500 m 20 m SQUID with input coil Josephson junctions Ketchen, Jaycox (1981) 16 of 45

17 Flux Noise in the SQUID V V o S (f) ( Φ 2 Hz -1 0 ) White noise 2 x Hz -1/ Frequency (Hz) 17 of 45

18 Superconducting Flux Transformer: Magnetometer B Closed superconducting circuit Magnetic field noise ~ THz -1/2 J SQUID Room temperature electronics 18 of 45

19 tesla Magnetic Fields 1 Conventional MRI Earth s field Urban noise Car at 50 m Human heart Fetal heart 1 femtotesla Human brain response SQUID magnetometer 19 of 45

20 The Diversity of SQUIDs 20 of 45

21 Quantum Design "Evercool" 21 of 45

22 High-T c SQUIDs Prospecting for Mineral Deposits Courtesy Cathy Foley, CSIRO 22 of 45

23 Gravity Probe-B Tests of General Relativity Geodetic effect curved space-time due to the presence of the Earth Lense-Thirring effect dragging of the local space-time frame due to rotation Courtesy Stanford University and NASA 23 of 45

24 MiniGRAIL: Gravitational Wave Antenna Lid Leiden Ui Universityit Spherical gravitational wave detector Temperature: 20 mk Diameter: 650 mm Resonance frequency: 3160 Hz Motion coupled to a transducer that amplifies the motion, and couples flux into a dc SQUID Quantum limited strain sensitivity: dl/l ~ of 45

25 SPT: South Pole Telescope Antarctica 9,500 feet 10 meter dish 960 Transition Edges Sensors with multiplexed SQUID readout SPT will survey 4,000 square degrees of sky in the next two years, and is expected to find large numbers of galaxy clusters. The Bullet Cluster 25 of 45

26 CardioMag Imaging System for Magnetocardiography 26 of 45

27 300-Channel SQUID Systems for Magnetoencephalography (MEG) 27 of 45

28 Ultralow Field Magnetic Resonance Imaging 28 of 45

29 High-Field Magnetic Resonance Imaging Magnetic field B 0 = 1.5 T Proton NMR frequency 0 64 MHz What if we were to lower the magnetic field and NMR frequency by a factor of 10 4? Courtesy GE, Inc. 29 of 45

30 ULF MRI Coil Geometry B x compensation coil Low noise cryostat containing SQUID Gradient coils B 0 coil (measurement field) B 1 coil (excitation field) B p coil (prepolarization field) B 0 = 132 T 0 = 5600 Hz Gradient fields define voxels in space in the same way as in high-field MRI 30 of 45

31 Three-Dimensional In Vivo Images of the Arm 20 mm 31 of 45

32 T 1 -Weighted Contrast Imaging If two different types of tissue have the same proton density, a conventional MRI pulse sequence may not distinguish them. T 1 depends strongly on the environment, and can be used to differentiate tissues types using a T 1 -contrast pulse sequence. T 1 contrast can be much higher in low fields than in high fields. 32 of 45

33 Measurements on Ex Vivo Prostate Tissue Malignant prostate removed surgically at UCSF hospital. Pathologist cuts two small tissue samples, one healthy and one cancerous (Blind: we do not know which is which). Samples rushed to Berkeley in a biohazard bag placed on ice. T 1 s measured: T 1A > T 1B Specimens are returned to UCSF where the pathologist characterizes a thin slice of each specimen. 33 of 45

34 Contrast (T 1A T 1B )/T 1A vs. % Difference in Tumor Content for each Specimen Pair (T 1A T 1B B)/T 1A δ = 35 patients (% tumor) B (% tumor) A T 1 (100% normal) = (1.43 ± 0.10) T 1 (100% tumor) Sufficient for in vivo T 1 -wighted contrast imaging 34 of 45

35 T 1-Map of Prostate Slice Dark lines indicate histology, which is performed on a thin slice. T 1 map is averaged over the entire thickness. Map clearly shows T 1 contrast Tissue identified through histological mapping Tissue is healthy unless labeled otherwise X + Y: Gleason score of tumors; 5 is the most advanced BPH: Benign Prostatic ti Hyperplasia GPS: Gland Poor Stroma 35 of 45

36 Outlook Microtesla MRI has the advantage of significantly higher T 1 contrast than high-field MRI. Other kinds of cancer: Do other types of tumors show T 1 contrast similar to that of prostate tumors? New funding to study ex vivo breast cancer National Institutes of Health provided funding to build a prototype system for in vivo imaging of prostate cancer. Next step: in vivo imaging g 36 of 45

37 Cold Dark Matter: The Hunt for the Axion 37 of 45

38 Cosmic Microwave Background: The Cosmic Rosetta Stone Neutrinos 0.6% Baryons (ordinary matter) 4.6% Dark Energy (DE) 73% Cold Dark Matter (CDM) 22% Thus 95% of the universe is unknown! 38 of 45

39 Cold Dark Matter A candidate particle is the axion, proposed in 1978 to explain the absence of a measurable electric dipole moment on the neutron Predicted mass: m a 1 ev 1meV(024- ( GHz) 39 of 45

40 Resonant Conversion of Axions into Photons Pierre Sikivie (1983) Primakoff Conversion HEMT* Amplifier Magnet Power Expected Signal ~ 10 6 Cavity Frequency *High Electron Mobility Transistor Need to scan frequency 40 of 45

41 Axion Detector at Lawrence Livermore National Laboratory Cooled to 1.5K 7 tesla magnet Scan Time Using a HEMT amplifier, time to scan the frequency range from 0.24 to 0.48 GHz: 270 years 41 of 45

42 Noise Temperatures of Two SQUID Amplifiers HEMT T N 2 K 702 MHz 684 MHz T QL = 33mK In the classical limit theory predicts T N T In the quantum limit: T QL = hf/k B Closest approach to quantum limit: At 799 MHz T N = 47 ± 5 mk T QL =38mK 42 of 45

43 Scan Time Using a HEMT amplifier, time to scan the frequency range from 0.24 to 0.48 GHz 270 years. The HEMT has been replaced with a SQUID amplifier. With the system cooled to 50 mk with a dilution refrigerator, time to scan the frequency range from 0.24 to 0.48 GHz 100 days. A SQUID amplifier was successfully operated on the axion detector at 1.5 K to demonstrate proof-of-principle. Given the success of this trial run, the Department of Energy has funded the installation of a dilution refrigerator to cool the cavity and SQUID to 50 mk. This will enable an effective search for the axion over the energy range 1 10 ev. 43 of 45

44 Epilogue SQUIDs are amazingly diverse, with applications in physics, chemistry, biology, medicine, materials science, geophysics, cosmology, quantum information,.. SQUIDs are remarkably broadband: 10 4 Hz (geophysics) to 10 9 Hz (axion detectors). The resolution of SQUID amplifiers is essentially limited by Heisenberg ss Uncertainty Principle. Microtesla MRI, the axion search, and a host of other applications, exist only because of the extraordinarily low noise of the SQUID which in itself seems to be a very tiny part of the whole system. 44 of 45

45 ULFMRI Thank You! Sarah Busch Erwin Hahn Michael Hatridge Nathan Kelso SeungKyun Lee Robert McDermott Michael Mössle Michael Mück Whit Myers Fredrik Öisjöen Alex Pines Dan Slichter Paul SanGiorgio Bennie ten Haken Andreas Trabesinger Travis Wong Koos Zevenhoven High Precision Devices Axion Detector S.J. Asztalos G. Carosi C. Hagmann D. Kinion, K. van Bibber M. Hotz L.J. Rosenberg G. Rybka, J. Hoskins J. Hwang P. Sikivie D. B. Tanner, R. Bradley 45 of 45